This invention relates to an electronic tuning block including a plurality of variable resistors for setting a preset voltage for use in an electronic tuning type television receiver or the like. More particularly, the present invention is directed to an electronic tuning block in which the arrangement of a plurality of screw drive type variable resistors on an insulating substrate is improved in order to reduce their space requirements and to reduce possible erroneous operation of the variable resistors.
Electronic tuning blocks of this kind are known and as schematically illustrated in FIGS. 1a through 1c typically include a box-shaped case 1 made of an insulating synthetic resin having its open lower surface fixed to an insulating substrate (not shown). Rectangular holes 2, 3 and 4 are formed on the upper surface of this case 1. Pointers 5 are fitted within the holes 2. As shown in FIG. 1b, these pointers 5 are movable integrally with sliders fitted to screw shafts 8 of variable resistors 9. The holes 3 guide and receive knobs 6 of slide switches for changing the frequency bands of the tuner, while the holes 4 receive rotary knobs 7 that are fitted to the end portions 8a of the screw shafts 8 of the variable resistors 9. Reference numeral 7a represents a sleeve which is integral with each knob 7 and reference numeral 10 denotes terminals.
According to the construction of such known devices, the variable resistors 9 are spaced equally and lie across the insulating substrate with their knobs 7 aligned on the same line. In order to insure smooth knob operation, therefore, a predetermined gap must be maintained between an adjacent pair of knobs 7, thus increasing the space needed along the insulating substrate in its longitudinal direction to accommodate the resistors 9. According to this arrangement, the adjacent knobs 7 are positioned in the path of movement of a finger that is operating the desired knob and, consequently, the knob adjacent the desired knob is likely to be erroneously manipulated.
To solve this problem, another construction has been proposed in which the positions of the rotary knobs 7 of the adjacent variable resistors 9 are deviated from one another and the knobs 7 are staggered in two lines so that parts thereof overlap with one another to reduce the space requirements, as illustrated in FIGS. 2a and 2b. In this case, however, two kinds of knobs 7 become necessary, one having a long sleeve 7a and the other, a shorter sleeve 7a'. This lowers productivity. In addition, since the knobs are aligned in two lines adjacent one another with parts thereof overlapping adjacent knobs 7 are still positioned in the path of movement of a finger operating a knob, and the desired knob is difficult to operate and the adjacent knobs are likely to be erroneously operated.